1. Field of the Invention
The present invention relates to a two-wheel drive/four-wheel drive switching system for a vehicle.
2. Description of Background Art
Heretofore, a vehicle which can switch between two wheel drive and four wheel drive is known.
FIGS. 8 to 10 show an example of the vehicle. The vehicle 1 shown in the drawings is mainly composed of a body frame 3 in the center of which an engine 2 is mounted, front wheels 4 and rear wheels 5 arranged on both sides of the front and the rear of the body frame 3, a steering handlebar 6 arranged on the upside of the front of the body frame 3 for steering the front wheels 4, a fuel tank 7 attached to the body frame 3 and a seat 8 attached in the rear of the fuel tank 7.
As shown in FIG. 9, each front wheel 4 is supported by a suspension 9 provided to both sides of the front of the body frame 3 so that each front wheel can fluctuate. Similarly, each rear wheel 5 is supported by a suspension 10 provided to both sides of the rear of the body frame 3 so that each rear wheel can fluctuate.
A final reduction gear unit for the front wheel 13 and a final reduction gear unit for the rear wheel 14 respectively coupled to the engine 2 via propeller shafts 11, 12 are provided in the center of the front and in the center of the rear of the body frame 3. The right and left front wheels 4 and the right and left rear wheels 5 are connected to the final reduction gear unit for the front wheel 13 and the final reduction gear unit for the rear wheel 14.
A two-wheel drive/four-wheel drive switching system for switching between a rear wheel drive state and a four wheel drive state by connecting or disconnecting power transmitted to the front wheels 4 is provided between the final reduction gear unit for the front wheel 13 and the front propeller shaft 11, for example.
Alternatively, the two-wheel drive/four-wheel drive switching system may be provided between the rear propeller shaft 12 and the final reduction gear unit for the rear wheel 14, in order to switch between a front wheel drive state and a four wheel drive state.
The driving states are suitably switched by a rider according to the condition of a road and the running speed.
FIG. 10 shows the proposed structure of this conventional two-wheel drive/four-wheel drive switching system.
A two-wheel drive/four-wheel drive switching system 15 in FIG. 10 is provided with a switching unit 18 for connecting or disconnecting an output shaft 33 of the final reduction gear unit for the front wheel 13 and the propeller shaft 11.
The switching unit 18 is installed in a casing 37 attached to the final reduction gear unit for the front wheel 13. The switching unit 18 is provided with an inner ring 41 fitted to the output shaft 33 via a spline as a driven shaft, an outer ring 38 supported by the casing 37 via a bearing 39 so that the outer ring can be revolved as a driving shaft, plural connecting/disconnecting members 34 inserted between the outer ring 38 and the inner ring 41 for connecting or disconnecting the outer ring 38 and the inner ring 41, a retainer 46 for holding the plural connecting/disconnecting members 34 so that they can be turned, and a hook plate 19 interlocked with the retainer 46. Also included is an electromagnetic coil 36 attached to the casing 37 around the output shaft 33 and a rotor 20 provided around the electromagnetic coil 36 and integrated with the outer ring 38. The switching unit connects the outer ring 38 and the inner ring 41 via the connecting/disconnecting members 34 by rotational resistance when the electromagnetic coil 36 attracts the hook plate 19 to the rotor 20.
An energizing cable 27 for supplying driving current is connected to the electromagnetic coil 36, pierces the side wall of the casing 37, and is led outside and is connected to a control unit 28 installed in a vehicle 1. FIG. 10 also shows a power source 29.
The two-wheel-drive/four-wheel drive switching system 15 configured as described above attracts the hook plate 19 to the rotor 20 by turning on the electromagnetic coil 36, connects the inner ring 41 and the outer ring 38 via the connecting/disconnecting members 34 by rotational resistance caused at that time. As a result, the propeller shaft 11 and the output shaft 33 are connected by connecting the outer ring 38 and the inner ring 41, thus transmitting the revolution of the engine 2 to the final reduction gear unit for the front wheel 13, and turning a two wheel drive state to a four wheel drive state.
Conversely, the switching unit disconnects the inner ring 41 and the outer ring 38 by disconnecting energizing to the electromagnetic coil 36 and releasing attraction for the hook plate 19, disconnects the transmission of power to the final reduction gear unit for the front wheel 13, thus turning a four wheel drive state to a two wheel drive state by only the rear wheels.
Such a conventional type two-wheel drive/four-wheel drive switching system 15 has the following problems to be improved.
Specifically, the energizing cable 27 for supplying driving current to the electromagnetic coil 36 is led outside the casing 37. Likewise, a coupler connected to control unit 28 is outside of the casing 37. The energizing cable 27 and the coupler compose accessories.
As the energizing cable 27 remains led outside the casing 37, work for fixing the accessories such as wiring and fixing the energizing cable 27 and fixing the coupler attached to the energizing cable 27 is required after the two-wheel drive/four-wheel drive switching system 15 is attached to the final reduction gear unit for the front wheel 13 and the work is troublesome.
Other components of vehicle 1 exist around the two-wheel drive/four-wheel drive switching system 15. These components include, for example, a tie rod and a pitman arm, respectively forming a steering mechanism arranged close around the final reduction gear unit for the front wheel 13. As a result, the position in which the energizing cable 27 is wired and fixed is restricted by these components.